For many people, the definition of a planet was only made clear in 2006, when the spunky world Pluto was demoted from a planet to a dwarf planet. Now, a team of astronomers is pushing for “planet” ...

What was discovered in Flagstaff, Arizona, and killed off in Prague? If you answered "Pluto's planethood," your grasp of the astronomical is excellent. Feb. 18 marks the 95th anniversary of the ...

For centuries, humans have gazed at the stars, trying to understand what lies beyond the familiar planets we know. From Mercury’s blazing orbit near the Sun to Neptune’s icy edge, our Solar System has ...

Astronomers are investigating a potential hidden planet, dubbed Planet Y, far beyond Neptune. Its gravitational pull is suspected to be causing unusual orbital tilts in distant Kuiper Belt Objects.

As elementary schoolers, we learned the order of the planets. Maybe your teacher even had a snappy mnemonic like “My Very Educated Mother Just Served Us Nine Pizzas” or “My Very Educated Mother Just ...

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights. Samantha Lawler, Assistant professor, Astronomy, ...

The year was 2015. After traveling billions and billions of miles through the Erebus, New Horizons encounters the boatman, and the somber lord of the departed. The spacecraft could have been called ...

Editor’s note: A version of this story originally appeared in Astronomy’s 2007 special issue 50 Greatest Mysteries of the Universe. For a more recent discussion of Pluto’s planethood, see “An ...

NASA has released a new video showing what it might be like to land on Pluto with a brand-new view of the dwarf planet's surface. The space agency’s New Horizons spacecraft spent about six weeks in a ...

Pluto may have lost its status as a full-fledged planet in 2006, but that doesn't mean it's a joke of a world this April Fools' Day and the folks behind Pluto TV want to make that clear. On April 1, ...